It is an understatement to say that literature dealing with timber, harvesting, sawing, and processing using chemicals for the preservation of timber is broad. It is vast. Timber which is used in substantial quantity in all parts of the civilized world is perhaps one of the most versatile known materials of construction, but has the disadvantage that it is perishable, despite a substantial natural durability of some woods. The properties of the wood, the natural durability, and its treatment, are well summarized in a BWPA Annual Convention Report, The Marketing of Treated Fencing In The British Isles, by C. S. Smith, wherein a substantial body of literature is identified and the state of the art in 1972 is well summarized, particularly in relation to the preservation of wood. Further annotation of the state of the art is to be found in a variety of publications of the Forest Products, Research Laboratory of England, United States Department of Agriculture, United States Forest Service, and a variety of their publications available through the United States Government Printing Office. Much is reported on the preservation of wood particularly with creosote in impregnation and various treatments involved in delaying the onset of fungal and bacterial deterioration of wood in use, particularly in moist areas, especially ground contact.
The problem of extending the life of wood in structures is important and much literature is also available in the annotation of the treatment of mill work and joinery and structural work which is used in the construction of homes. This type of material is to be found in the patent literature where it is conveniently classified in Class 117, subclasses 116 and 117, in the United States Patent Office; particularly where some effort has been made at the total impregnation of wood reference can be had to any of the following United States Patents:
285,087 September 18, 1883 G. S. Valentine 609,442, August 23, 1898 G. F. Lebioda 645,793, March 20, 1900 C. J. Doyle 836,592 November 20, 1906 J. T. Logan 917,265 April 6, 1909 B. Diamand 1,146,501 July 13, 1915 H. G. Jennison 1,422,119 July 11, 1922 Meyer - Walsh 1,602,417 October 12, 1926 G. B. Shipley 1,602,933 October 12, 1926 R. D. Prittie 1,631,532 June 7, 1927 A. G. Howerton 1,697,248 January 1, 1929 Lauter 2,039,393 May 5, 1936 J. R. Coolidge et al 2,947,648 August 2, 1960 L. F. Sonnabend et al 2,740,728 April 3, 1956 L. F. Sonnabend et al
Other literature available through British Forest Products Research Laboratories is as follows:
"The Preservative Treatment Of Home-Grown Timbers by Diffusion", D. N. Smith and R. Cockcroft, reprinted from `WOOD`, Vol. 26, pp. 490-492, December 1961.
"Selecting A Preservative Treatment To Incorporate In The Manufacture of Joinery", Ministry of Technology.
"Ensuring Good Service Life For Window Joinery", Technical Note No. 29, May 1968.
"The Natural Durability Classification Of Timber ", Technical Note No. 40, October 1969.
"Preservation Of Building Timbers By Boron Diffusion Treatment", Technical Note No. 41, October 1969.
"Preservative Treatments For External Softwood Joinery Timber", Technical Note No. 24, Revised April 1971.
"Timber Preservatives and Methods of Treatment", R. Cockcroft, Timberlab Papers, No. 46, 1971.
"Wood Preservation By The Boron Diffusion Process - The Effect Of Moisture Content On Diffusion Time", D. B. Smith and A. I. Williams, Timberlab Papers, No. 5, 1969.
"The Comparative Resistance To Fire Of Various Species Of Timbers", J. Bryan and J. S. Doman, reprinted from `WOOD`, January 1940.
"Factors Affecting The Introduction Of Preservatives Into Wood", W. B. Banks, Pestic. Sci. 219-227, 1972.
"Wood Treatment Resin Forming Systems", United States Department of Agriculture, United States Forest Service, Booklet R 1703.
"Resin Treated Wood", United States Department of Agriculture, United States Forest Service, Booklet 1380.
While the literature on the subject is extensive and the general principle is recognized that wood is porous and that it should be possible to penetrate the wood with preservatives and resin components, actual practice in the art as known in 1972 indicates that even under extreme vacuum and pressure conditions, whether the wood be positioned horizontally or vertically in the impregnation tank, the usual impregnation runs into the heart wood hardly more than a few millimeters. Accordingly, specifications generally call for treatment of pieces which have been sawed to dimension and if they are sawed on the site of construction specifications call for treatment of the fresh cut areas.
It is in this light that it is apparent that a process which actually reliably penetrates timber or wood with resins, preservatives, or flame retarding agents and the process for so doing constitutes a genuine positive contribution to the art.
It is, accordingly, the object of this invention to provide a process for the production of fully impregnated wood, the wood being impregnated to its core with resin components, e.g. phenol-formaldehyde and variants, together with preservatives which can be surplus formaldehyde and flame retarding agents which can be known, or novel, based on organic halogen compounds.
Other objects and advantages of the invention will in part be obvious and in part appear hereinafter from the consideration of the details of the process as it is related to type woods.